The debt office, which is a unit of the Central Bank said 15 billion rupees of bills were offered to the auction and only 10 billion rupees of bids were accepted.

If bids are not accepted the central bank can buy them or offer 'on tap' later.

Analysts say if the Central Bank buys bill it creates new demand in the economy and puts pressure on the balance of payments.

Offering on taps also distorts secondary market trading preventing the establishment of a true market rate, which can help draw more money to bill markets and maintain macro-economic stability.

When rates fell two weeks ago amid excess liquidity in interbank markets analysts had urged the central bank to sell down its bill stock and mop up liquidity to prevent renewed pressure on a dollar peg from unsterilized purchases of foreign exchange.

But even a small rise in interest rates may help the economy stabilize, analysts say.

Analysts say while the central bank has been quick to sterilize foreign exchange sales with outright purchases of bills, which weakens the dollar peg, it has been less willing to sell bills outright to withdraw the liquidity to strengthen the peg when the opportunity arose.

Bill rates are however above the reverse repo policy rate now.

In the secondary market 3-month bills were quoted around 10.95/11.10 percent, six months 12.25/35 percent and the one 12.60/70 percent, dealers said.

In the morning call money topped 10.75 percent the highest in recent months, while gilt backed repos were quoted around 9.50 percent.

In late Wednesday trading the spot US dollar traded stronger around 131.90/132.00 rupees after opening around 132.50 levels earlier in the day. The rupee strengthened as much as 131.40/50 against the spot dollar in intra-day trading.

Update II